An aneurysm is an abnormal bulge or ballooning of the wall of a blood vessel, which most commonly occurs in arterial blood vessels. Aneurysms typically form at a weakened point of a wall of a blood vessel. The force of the blood pressure against the weakened wall causes the wall to abnormally bulge or balloon outwardly. Aneurysms, particularly cranial aneurysms, are a serious medical condition because an aneurysm can apply undesired pressure to areas within the brain. Additionally, there is the possibility that the aneurysm may rupture or burst leading to serious medical complications including mortality.
When a patient is diagnosed with an unruptured aneurysm, the aneurysm is treated in an attempt to prevent the aneurysm from rupturing. Unruptured aneurysms have traditionally been treated by what is known as “clipping.” Clipping requires an invasive surgical procedure wherein the surgeon makes incisions into the patient's body to access the afflicted blood vessel. Once the surgeon has accessed the aneurysm, he or she places a clip around the neck of the aneurysm to block the flow of blood into the aneurysm which prevents the aneurysm from rupturing. While clipping may be an acceptable treatment for some aneurysms, there is a considerable amount of risk involved with employing the clipping procedure to treat cranial aneurysms because such procedures require open brain surgery.
More recently, intravascular catheter techniques have been used to treat cranial aneurysms because such techniques do not require cranial or skull incisions, i.e., these techniques do not require open brain surgery. Typically, these techniques involve using a catheter to deliver embolic devices to a preselected location within the vasculature. For example, in the case of a cranial aneurysm, methods and procedure, which are well known in the art, are used for inserting the distal end of a delivery catheter into the vasculature of a patient and guiding the catheter through the vasculature to the site of the cranial aneurysm. A vascular occlusion device is then attached to the end of a pusher member which pushes the occlusion device through the catheter and out of the distal end of the catheter where the occlusion device is delivered into the aneurysm.
Once the occlusion device has been deployed within the aneurysm, the blood clots on the occlusion device and forms a thrombus. The thrombus forms an occlusion which seals off the aneurysm, preventing further ballooning or rupture. The deployment procedure is repeated until the desired number of occlusion devices are deployed within the aneurysm. Typically, it is desired to deploy enough coils to obtain a packing density of about 20% or more, preferably about 35% and more if possible.
The most common vascular occlusion device is an embolic coil. Embolic coils are typically constructed from a metal wire which has been twisted into a helical shape. One of the drawbacks of embolic coils is that they do not provide a large surface area for the blood to clot. Additionally, the embolic coil may be situated in such a way that there are relatively considerable gaps between adjacent coils in which blood may freely flow. The addition of extra coils into the aneurysm does not always solve this problem because deploying too many coils into the aneurysm may lead to an undesired rupture.
Therefore, there remains a need that is recognized and addressed according to the present invention for an occlusion device which provides a greater surface area to promote blood clotting, and also effectively occupies the space between adjacent occlusion devices without increasing the risk of rupturing the aneurysm.